Soumya Shreeram

The hot phase of the circumgalactic medium (CGM) allows us to probe the inflow and outflow of gas responsible for dictating the evolution of a galaxy’s structure. In this talk, I will present my work on using the TNG300 hydrodynamical simulations to build a fully self-consistent forward model for the hot CGM. To do that, I construct a lightcone and generate mock X-ray observations of the large-scale structure. I quantify the main projection effects impacting CGM measurements, namely the locally correlated large-scale structure in X-rays and the effect due to satellite galaxies hosted by more massive halos, which affect the measured hot CGM galactocentric profiles in stacking experiments. Recent eROSITA measurements of the radial profiles of the hot CGM in the Milky-Way stellar mass (MW-mass) regime provide us with a new benchmark to constrain the hot gas around MW-mass central and satellite galaxies and their halo mass distributions. I will also present recent results (Shreeram et al. 2025b) on applying the TNG-based forward model to the stacked X-ray radial surface brightness profile measured by eROSITA around MW-mass galaxies. My work shows how the gas physics is responsible for driving the shape of the observed hot CGM (in stellar-mass-selected X-ray stacking experiments) is tightly correlated by the underlying halo-mass distribution. My talk also delivers a novel technique to constrain the AGN X-ray luminosity jointly with the radial hot CGM gas distribution within the halo using measurements from X-ray galaxy stacking experiments. Implementing this technique on other state-of-the-art simulations will provide a new ground for testing different galaxy formation models with observations. Lastly, I will also discuss the impact of the Large Scale Structure on the CGM (Shreeram et al. 2025c), where we test how the CGM properties are affected based on their location in the cosmic web.